Rewrite the entire code-base

The following changes are focused upon:
- Modularity
- Doing away with globals
- No heap allocations
- Better command line interface
- Switch from Xlib to XCB
- More verbose type definitions
- Implement a single-file config by utilising X-macros

.clang-format

@@ -1,6 +1,8 @@
 BasedOnStyle: Google
 IndentWidth: 4
+InsertBraces: true
 ColumnLimit: 79
-AlignArrayOfStructures: Left
-AlignConsecutiveMacros: true
+AlignConsecutiveMacros: Consecutive
 AllowShortFunctionsOnASingleLine: None
+AllowShortLoopsOnASingleLine: false
+AllowShortIfStatementsOnASingleLine: Never

.clangd

@@ -1,6 +1,5 @@
-CompileFlags:
-  Add:
-    - "-I."
-    - "-I./inc"
-    - "-I.."
-    - "-I../inc"
+Diagnostics:
+  UnusedIncludes: Strict
+  MissingIncludes: Strict
+  Includes:
+    IgnoreHeader: bits/getopt_core.h

.gitignore

@@ -1,3 +1,3 @@
 build/
 .cache/
-dwmblocks
+compile_commands.json

Makefile

@@ -3,18 +3,20 @@
 BIN := dwmblocks
 BUILD_DIR := build
 SRC_DIR := src
-INC_DIR := inc
+INC_DIR := include
 
 VERBOSE := 0
+LIBS := xcb-atom
 
 PREFIX := /usr/local
-CFLAGS := -Wall -Wextra -Ofast -I. -I$(INC_DIR)
-CFLAGS += -Wall -Wextra -Wno-missing-field-initializers
-LDLIBS := -lX11
+CFLAGS := -Ofast -I. -I$(INC_DIR)
+CFLAGS += -DBINARY=\"$(BIN)\" -D_POSIX_C_SOURCE=200809L
+CFLAGS += -Wall -Wpedantic -Wextra -Wswitch-enum
+CFLAGS += $(shell pkg-config --cflags $(LIBS))
+LDLIBS := $(shell pkg-config --libs $(LIBS))
 
-VPATH := $(SRC_DIR)
-OBJS := $(patsubst $(SRC_DIR)/%.c,$(BUILD_DIR)/%.o,$(wildcard $(SRC_DIR)/*.c))
-OBJS += $(patsubst %.c,$(BUILD_DIR)/%.o,$(wildcard *.c))
+SRCS := $(wildcard $(SRC_DIR)/*.c)
+OBJS := $(subst $(SRC_DIR)/,$(BUILD_DIR)/,$(SRCS:.c=.o))
 
 INSTALL_DIR := $(DESTDIR)$(PREFIX)/bin
 
@@ -26,17 +28,15 @@ endif
 
 all: $(BUILD_DIR)/$(BIN)
 
-$(BUILD_DIR)/$(BIN): $(OBJS)
-	$(PRINTF) "LD" $@
-	$Q$(LINK.o) $^ $(LDLIBS) -o $@
-
-$(BUILD_DIR)/%.o: %.c config.h | $(BUILD_DIR)
+$(BUILD_DIR)/%.o: $(SRC_DIR)/%.c config.h
+	$Qmkdir -p $(@D)
 	$(PRINTF) "CC" $@
 	$Q$(COMPILE.c) -o $@ $<
 
-$(BUILD_DIR):
-	$(PRINTF) "MKDIR" $@
-	$Qmkdir -p $@
+
+$(BUILD_DIR)/$(BIN): $(OBJS)
+	$(PRINTF) "LD" $@
+	$Q$(LINK.o) $^ $(LDLIBS) -o $@
 
 clean:
 	$(PRINTF) "CLEAN" $(BUILD_DIR)

README.md

@@ -85,15 +85,14 @@ dwmblocks &
 
 ### Modifying the blocks
 
-You can define your status bar blocks in `config.c`:
+You can define your status bar blocks in `config.h`:
 
 ```c
-Block blocks[] = {
+#define BLOCKS(X) \
     ...
-    {"volume", 0,    5},
-    {"date",   1800, 1},
+    X("volume", 0, 5), \
+    X("date", 1800, 1), \
     ...
-}
 ```
 
 Each block has the following properties:
@@ -107,17 +106,21 @@ Each block has the following properties:
 Apart from defining the blocks, features can be toggled through `config.h`:
 
 ```c
-// Maximum possible length of output from block, expressed in number of characters.
-#define CMDLENGTH 50
-
-// The status bar's delimiter that appears in between each block.
+// String used to delimit block outputs in the status.
 #define DELIMITER "  "
 
-// Adds a leading delimiter to the status bar, useful for powerline.
-#define LEADING_DELIMITER 1
+// Maximum number of Unicode characters that a block can output.
+#define MAX_BLOCK_OUTPUT_LENGTH 45
 
-// Enable clickability for blocks. See the "Clickable blocks" section below.
+
+// Control whether blocks are clickable.
 #define CLICKABLE_BLOCKS 1
+
+// Control whether a leading delimiter should be prepended to the status.
+#define LEADING_DELIMITER 0
+
+// Control whether a trailing delimiter should be appended to the status.
+#define TRAILING_DELIMITER 0
 ```
 
 ### Signalling changes

config.c

@@ -1,19 +0,0 @@
-#include "config.h"
-
-#include "block.h"
-#include "util.h"
-
-Block blocks[] = {
-    {"sb-mail",    600,  1 },
-    {"sb-music",   0,    2 },
-    {"sb-disk",    1800, 3 },
-    {"sb-memory",  10,   4 },
-    {"sb-loadavg", 5,    5 },
-    {"sb-mic",     0,    6 },
-    {"sb-record",  0,    7 },
-    {"sb-volume",  0,    8 },
-    {"sb-battery", 5,    9 },
-    {"sb-date",    1,    10},
-};
-
-const unsigned short blockCount = LEN(blocks);

config.h

@@ -1,6 +1,29 @@
 #pragma once
 
-#define CLICKABLE_BLOCKS  1     // Enable clickability for blocks
-#define CMDLENGTH         45    // Trim block output to this length
-#define DELIMITER         "  "  // Delimiter string used to separate blocks
-#define LEADING_DELIMITER 0     // Whether a leading separator should be used
+// String used to delimit block outputs in the status.
+#define DELIMITER "  "
+
+// Maximum number of Unicode characters that a block can output.
+#define MAX_BLOCK_OUTPUT_LENGTH 45
+
+// Control whether blocks are clickable.
+#define CLICKABLE_BLOCKS 1
+
+// Control whether a leading delimiter should be prepended to the status.
+#define LEADING_DELIMITER 0
+
+// Control whether a trailing delimiter should be appended to the status.
+#define TRAILING_DELIMITER 0
+
+// Define blocks for the status feed as X(cmd, interval, signal).
+#define BLOCKS(X)         \
+    X("sb-mail", 600, 1)  \
+    X("sb-music", 0, 2)   \
+    X("sb-disk", 1800, 3) \
+    X("sb-memory", 10, 4) \
+    X("sb-loadavg", 5, 5) \
+    X("sb-mic", 0, 6)     \
+    X("sb-record", 0, 7)  \
+    X("sb-volume", 0, 8)  \
+    X("sb-battery", 5, 9) \
+    X("sb-date", 1, 10)

inc/bar.h

@@ -1,15 +0,0 @@
-#pragma once
-#include "block.h"
-#include "config.h"
-#include "util.h"
-
-typedef struct {
-    char *current;
-    char *previous;
-} BarStatus;
-
-extern unsigned short debugMode;
-
-void initStatus(BarStatus *);
-void freeStatus(BarStatus *);
-void writeStatus(BarStatus *);

inc/block.h

@@ -1,17 +0,0 @@
-#pragma once
-#include "config.h"
-
-typedef struct {
-    const char *command;
-    const unsigned int interval;
-    const unsigned int signal;
-    int pipe[2];
-    char output[CMDLENGTH * 4 + 1];
-} Block;
-
-extern Block blocks[];
-extern const unsigned short blockCount;
-
-void execBlock(const Block *, const char *);
-void execBlocks(unsigned int);
-void updateBlock(Block *);

inc/util.h

@@ -1,8 +0,0 @@
-#pragma once
-
-#define LEN(arr)  (sizeof(arr) / sizeof(arr[0]))
-#define MAX(a, b) (a > b ? a : b)
-
-int gcd(int, int);
-void closePipe(int[2]);
-void trimUTF8(char*, unsigned int);

inc/x11.h

@@ -1,5 +0,0 @@
-#pragma once
-
-int setupX();
-int closeX();
-void setXRootName(char *);

include/block.h

@@ -0,0 +1,24 @@
+#pragma once
+
+#include <bits/stdint-uintn.h>
+#include <stdbool.h>
+#include <sys/types.h>
+
+#include "config.h"
+#include "util.h"
+
+typedef struct {
+    const char *const command;
+    const unsigned int interval;
+    const int signal;
+
+    int pipe[PIPE_FD_COUNT];
+    char output[MAX_BLOCK_OUTPUT_LENGTH * UTF8_MAX_BYTE_COUNT + 1];
+    pid_t fork_pid;
+} block;
+
+int block_init(block *const block);
+int block_deinit(block *const block);
+int block_execute(block *const block, const uint8_t button);
+int block_update(block *const block);
+bool block_must_run(const block *const block, const unsigned int time);

include/cli.h

@@ -0,0 +1,10 @@
+#pragma once
+
+#include <stdbool.h>
+
+typedef struct {
+    bool is_debug_mode;
+} cli_arguments;
+
+int cli_init(cli_arguments* const args, const char* const argv[],
+             const int argc);

include/main.h

@@ -0,0 +1,14 @@
+#pragma once
+
+#include <signal.h>
+
+#include "block.h"
+#include "config.h"
+#include "util.h"
+
+// Utilise C's adjacent string concatenation to count the number of blocks.
+#define X(...) "."
+extern block blocks[LEN(BLOCKS(X)) - 1];
+#undef X
+
+#define REFRESH_SIGNAL SIGUSR1

include/signal-handler.h

@@ -0,0 +1,22 @@
+#pragma once
+
+#include <bits/types/sigset_t.h>
+
+#include "timer.h"
+
+typedef sigset_t signal_set;
+typedef int (*signal_refresh_callback)(void);
+typedef int (*signal_timer_callback)(timer* const timer);
+
+typedef struct {
+    int fd;
+    const signal_refresh_callback refresh_callback;
+    const signal_timer_callback timer_callback;
+} signal_handler;
+
+signal_handler signal_handler_new(
+    const signal_refresh_callback refresh_callback,
+    const signal_timer_callback timer_callback);
+int signal_handler_init(signal_handler* const handler);
+int signal_handler_deinit(signal_handler* const handler);
+int signal_handler_process(signal_handler* const handler, timer* const timer);

include/status.h

@@ -0,0 +1,25 @@
+#pragma once
+
+#include <stdbool.h>
+
+#include "block.h"
+#include "config.h"
+#include "main.h"
+#include "util.h"
+#include "x11.h"
+
+typedef struct {
+#define STATUS_LENGTH                                                        \
+    ((LEN(blocks) * (MEMBER_LENGTH(block, output) - 1) + CLICKABLE_BLOCKS) + \
+     (LEN(blocks) - 1 + LEADING_DELIMITER + TRAILING_DELIMITER) *            \
+         (LEN(DELIMITER) - 1) +                                              \
+     1)
+    char current[STATUS_LENGTH];
+    char previous[STATUS_LENGTH];
+#undef STATUS_LENGTH
+} status;
+
+status status_new(void);
+bool status_update(status* const status);
+int status_write(const status* const status, const bool is_debug_mode,
+                 x11_connection* const connection);

include/timer.h

@@ -0,0 +1,14 @@
+#pragma once
+
+#include <signal.h>
+
+#define TIMER_SIGNAL SIGALRM
+
+typedef struct {
+    unsigned int time;
+    const unsigned int tick;
+    const unsigned int reset_value;
+} timer;
+
+timer timer_new(void);
+int timer_arm(timer *const timer);

include/util.h

@@ -0,0 +1,22 @@
+#pragma once
+
+#include <stddef.h>
+
+#define MAX(a, b)                 ((a) > (b) ? (a) : (b))
+#define LEN(arr)                  (sizeof(arr) / sizeof(arr[0]))
+#define BIT(n)                    (1 << (n))
+#define MEMBER_SIZE(type, member) sizeof(((type*)NULL)->member)
+#define MEMBER_LENGTH(type, member) \
+    (MEMBER_SIZE(type, member) / MEMBER_SIZE(type, member[0]))
+
+#define UTF8_MAX_BYTE_COUNT 4
+
+enum pipe_fd_index {
+    READ_END,
+    WRITE_END,
+    PIPE_FD_COUNT,
+};
+
+unsigned int gcd(unsigned int a, unsigned int b);
+size_t truncate_utf8_string(char* const buffer, const size_t size,
+                            const size_t char_limit);

include/watcher.h

@@ -0,0 +1,22 @@
+#pragma once
+
+#include <stdbool.h>
+#include <sys/poll.h>
+
+#include "main.h"
+#include "util.h"
+
+typedef enum {
+    SIGNAL_FD = LEN(blocks),
+    WATCHER_FD_COUNT,
+} watcher_fd_index;
+
+typedef struct pollfd watcher_fd;
+
+typedef struct {
+    watcher_fd fds[WATCHER_FD_COUNT];
+} watcher;
+
+int watcher_init(watcher *const watcher, const int signal_fd);
+int watcher_poll(watcher *const watcher, const int timeout_ms);
+bool watcher_fd_is_readable(const watcher_fd *const watcher_fd);

include/x11.h

@@ -0,0 +1,10 @@
+#pragma once
+
+#include <xcb/xcb.h>
+
+typedef xcb_connection_t x11_connection;
+
+x11_connection* x11_connection_open(void);
+void x11_connection_close(x11_connection* const connection);
+int x11_set_root_name(x11_connection* const connection,
+                      const char* const name);

src/bar.c

@@ -1,62 +0,0 @@
-#include "bar.h"
-
-#include <stdio.h>
-#include <stdlib.h>
-#include <string.h>
-
-#include "block.h"
-#include "x11.h"
-
-void initStatus(BarStatus *status) {
-    const unsigned int statusLength =
-        (blockCount * (LEN(blocks[0].output) - 1)) +
-        (blockCount - 1 + LEADING_DELIMITER) * (LEN(DELIMITER) - 1);
-
-    status->current = (char *)malloc(statusLength);
-    status->previous = (char *)malloc(statusLength);
-    status->current[0] = '\0';
-    status->previous[0] = '\0';
-}
-
-void freeStatus(BarStatus *status) {
-    free(status->current);
-    free(status->previous);
-}
-
-int updateStatus(BarStatus *status) {
-    strcpy(status->previous, status->current);
-    status->current[0] = '\0';
-
-    for (int i = 0; i < blockCount; i++) {
-        Block *block = blocks + i;
-
-        if (strlen(block->output)) {
-#if LEADING_DELIMITER
-            strcat(status->current, DELIMITER);
-#else
-            if (status->current[0]) strcat(status->current, DELIMITER);
-#endif
-
-#if CLICKABLE_BLOCKS
-            if (!debugMode && block->signal) {
-                char signal[] = {block->signal, '\0'};
-                strcat(status->current, signal);
-            }
-#endif
-
-            strcat(status->current, block->output);
-        }
-    }
-    return strcmp(status->current, status->previous);
-}
-
-void writeStatus(BarStatus *status) {
-    // Only write out if status has changed
-    if (!updateStatus(status)) return;
-
-    if (debugMode) {
-        printf("%s\n", status->current);
-        return;
-    }
-    setXRootName(status->current);
-}

src/block.c

@@ -1,72 +1,147 @@
 #include "block.h"
 
-#define _GNU_SOURCE
+#include <bits/stdint-uintn.h>
+#include <bits/types/FILE.h>
+#include <stdbool.h>
+#include <stddef.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <sys/types.h>
+#include <sys/wait.h>
 #include <unistd.h>
 
+#include "config.h"
 #include "util.h"
 
-static int execLock = 0;
+int block_init(block *const block) {
+    if (pipe(block->pipe) != 0) {
+        (void)fprintf(stderr,
+                      "error: could not create a pipe for \"%s\" block\n",
+                      block->command);
+        return 1;
+    }
 
-void execBlock(const Block *block, const char *button) {
-    unsigned short i = block - blocks;
+    block->fork_pid = -1;
 
-    // Ensure only one child process exists per block at an instance
-    if (execLock & 1 << i) return;
-    // Lock execution of block until current instance finishes execution
-    execLock |= 1 << i;
+    return 0;
+}
 
-    if (fork() == 0) {
-        close(block->pipe[0]);
-        dup2(block->pipe[1], STDOUT_FILENO);
-        close(block->pipe[1]);
+int block_deinit(block *const block) {
+    int status = close(block->pipe[READ_END]);
+    status |= close(block->pipe[WRITE_END]);
+    if (status != 0) {
+        (void)fprintf(stderr, "error: could not close \"%s\" block's pipe\n",
+                      block->command);
+        return 1;
+    }
 
-        if (button) setenv("BLOCK_BUTTON", button, 1);
+    return 0;
+}
 
-        FILE *file = popen(block->command, "r");
-        if (!file) {
-            printf("\n");
+int block_execute(block *const block, const uint8_t button) {
+    // Ensure only one child process exists per block at an instance.
+    if (block->fork_pid != -1) {
+        return 0;
+    }
+
+    block->fork_pid = fork();
+    if (block->fork_pid == -1) {
+        (void)fprintf(
+            stderr, "error: could not create a subprocess for \"%s\" block\n",
+            block->command);
+        return 1;
+    }
+
+    if (block->fork_pid == 0) {
+        const int write_fd = block->pipe[WRITE_END];
+        int status = close(block->pipe[READ_END]);
+
+        if (button != 0) {
+            char button_str[4];
+            (void)snprintf(button_str, LEN(button_str), "%hhu", button);
+            status |= setenv("BLOCK_BUTTON", button_str, 1);
+        }
+
+        const char null = '\0';
+        if (status != 0) {
+            (void)write(write_fd, &null, sizeof(null));
             exit(EXIT_FAILURE);
         }
 
-        // Buffer will hold both '\n' and '\0'
-        char buffer[LEN(block->output) + 1];
-        if (fgets(buffer, LEN(buffer), file) == NULL) {
-            // Send an empty line in case of no output
-            printf("\n");
+        FILE *const file = popen(block->command, "r");
+        if (file == NULL) {
+            (void)write(write_fd, &null, sizeof(null));
+            exit(EXIT_FAILURE);
+        }
+
+        // Ensure null-termination since fgets() will leave buffer untouched on
+        // no output.
+        char buffer[LEN(block->output)] = {[0] = null};
+        (void)fgets(buffer, LEN(buffer), file);
+
+        // Remove trailing newlines.
+        const size_t length = strcspn(buffer, "\n");
+        buffer[length] = null;
+
+        // Exit if command execution failed or if file could not be closed.
+        if (pclose(file) != 0) {
+            (void)write(write_fd, &null, sizeof(null));
+            exit(EXIT_FAILURE);
+        }
+
+        const size_t output_size =
+            truncate_utf8_string(buffer, LEN(buffer), MAX_BLOCK_OUTPUT_LENGTH);
+        (void)write(write_fd, buffer, output_size);
+
         exit(EXIT_SUCCESS);
     }
-        pclose(file);
 
-        // Trim to the max possible UTF-8 capacity
-        trimUTF8(buffer, LEN(buffer));
-
-        printf("%s\n", buffer);
-        exit(EXIT_SUCCESS);
-    }
+    return 0;
 }
 
-void execBlocks(unsigned int time) {
-    for (int i = 0; i < blockCount; i++) {
-        const Block *block = blocks + i;
-        if (time == 0 ||
-            (block->interval != 0 && time % block->interval == 0)) {
-            execBlock(block, NULL);
-        }
-    }
-}
-
-void updateBlock(Block *block) {
+int block_update(block *const block) {
     char buffer[LEN(block->output)];
-    int bytesRead = read(block->pipe[0], buffer, LEN(buffer));
 
-    // String from pipe will always end with '\n'
-    buffer[bytesRead - 1] = '\0';
-
-    strcpy(block->output, buffer);
-
-    // Remove execution lock for the current block
-    execLock &= ~(1 << (block - blocks));
+    const ssize_t bytes_read =
+        read(block->pipe[READ_END], buffer, LEN(buffer));
+    if (bytes_read == -1) {
+        (void)fprintf(stderr,
+                      "error: could not fetch output of \"%s\" block\n",
+                      block->command);
+        return 2;
+    }
+
+    // Collect exit-status of the subprocess to avoid zombification.
+    int fork_status = 0;
+    if (waitpid(block->fork_pid, &fork_status, 0) == -1) {
+        (void)fprintf(stderr,
+                      "error: could not obtain exit status for \"%s\" block\n",
+                      block->command);
+        return 2;
+    }
+    block->fork_pid = -1;
+
+    if (fork_status != 0) {
+        (void)fprintf(stderr,
+                      "error: \"%s\" block exited with non-zero status\n",
+                      block->command);
+        return 1;
+    }
+
+    (void)strcpy(block->output, buffer);
+
+    return 0;
+}
+
+bool block_must_run(const block *const block, const unsigned int time) {
+    if (time == 0) {
+        return true;
+    }
+
+    if (block->interval == 0) {
+        return false;
+    }
+
+    return time % block->interval == 0;
 }

src/cli.c

@@ -0,0 +1,30 @@
+#include "cli.h"
+
+#include <getopt.h>
+#include <stdbool.h>
+#include <stdio.h>
+
+int cli_init(cli_arguments *const args, const char *const argv[],
+             const int argc) {
+    args->is_debug_mode = false;
+
+    int opt = -1;
+    opterr = 0;  // Suppress getopt's built-in invalid opt message
+    while ((opt = getopt(argc, (char *const *)argv, "dh")) != -1) {
+        switch (opt) {
+            case 'd':
+                args->is_debug_mode = true;
+                break;
+            case 'h':
+                // fall through
+            case '?':
+                (void)fprintf(stderr, "error: unknown option `-%c'\n", optopt);
+                // fall through
+            default:
+                (void)fprintf(stderr, "usage: %s [-d]\n", BINARY);
+                return 1;
+        }
+    }
+
+    return 0;
+}

src/main.c

@@ -1,157 +1,180 @@
-#define _GNU_SOURCE
-#include <signal.h>
-#include <stdio.h>
-#include <string.h>
-#include <sys/epoll.h>
-#include <sys/signalfd.h>
+#include "main.h"
+
+#include <stdbool.h>
+#include <stddef.h>
 
-#include "bar.h"
 #include "block.h"
+#include "cli.h"
+#include "config.h"
+#include "signal-handler.h"
+#include "status.h"
+#include "timer.h"
 #include "util.h"
+#include "watcher.h"
 #include "x11.h"
 
-static unsigned short statusContinue = 1;
-unsigned short debugMode = 0;
-static int epollFD, signalFD;
-static unsigned int timerTick = 0, maxInterval = 1;
+#define BLOCK(cmd, period, sig) \
+    {                           \
+        .command = cmd,         \
+        .interval = period,     \
+        .signal = sig,          \
+    },
 
-void signalHandler() {
-    struct signalfd_siginfo info;
-    read(signalFD, &info, sizeof(info));
-    unsigned int signal = info.ssi_signo;
+block blocks[] = {BLOCKS(BLOCK)};
+#undef BLOCK
 
-    static unsigned int timer = 0;
-    switch (signal) {
-        case SIGALRM:
-            // Schedule the next timer event and execute blocks
-            alarm(timerTick);
-            execBlocks(timer);
-
-            // Wrap `timer` to the interval [1, `maxInterval`]
-            timer = (timer + timerTick - 1) % maxInterval + 1;
-            return;
-        case SIGUSR1:
-            // Update all blocks on receiving SIGUSR1
-            execBlocks(0);
-            return;
-    }
-
-    for (int j = 0; j < blockCount; j++) {
-        const Block *block = blocks + j;
-        if (block->signal == signal - SIGRTMIN) {
-            char button[4];  // value can't be more than 255;
-            sprintf(button, "%d", info.ssi_int & 0xff);
-            execBlock(block, button);
-            break;
-        }
-    }
-}
-
-void termHandler() {
-    statusContinue = 0;
-}
-
-void setupSignals() {
-    sigset_t handledSignals;
-    sigemptyset(&handledSignals);
-    sigaddset(&handledSignals, SIGUSR1);
-    sigaddset(&handledSignals, SIGALRM);
-
-    // Append all block signals to `handledSignals`
-    for (int i = 0; i < blockCount; i++)
-        if (blocks[i].signal > 0)
-            sigaddset(&handledSignals, SIGRTMIN + blocks[i].signal);
-
-    // Create a signal file descriptor for epoll to watch
-    signalFD = signalfd(-1, &handledSignals, 0);
-
-    // Block all realtime and handled signals
-    for (int i = SIGRTMIN; i <= SIGRTMAX; i++) sigaddset(&handledSignals, i);
-    sigprocmask(SIG_BLOCK, &handledSignals, NULL);
-
-    // Handle termination signals
-    signal(SIGINT, termHandler);
-    signal(SIGTERM, termHandler);
-
-    // Avoid zombie subprocesses
-    struct sigaction signalAction;
-    signalAction.sa_handler = SIG_DFL;
-    sigemptyset(&signalAction.sa_mask);
-    signalAction.sa_flags = SA_NOCLDWAIT;
-    sigaction(SIGCHLD, &signalAction, 0);
-}
-
-void statusLoop() {
-    // Update all blocks initially
-    raise(SIGALRM);
-
-    BarStatus status;
-    initStatus(&status);
-    struct epoll_event events[blockCount + 1];
-    while (statusContinue) {
-        int eventCount = epoll_wait(epollFD, events, LEN(events), 100);
-        for (int i = 0; i < eventCount; i++) {
-            unsigned short id = events[i].data.u32;
-            if (id < blockCount) {
-                updateBlock(blocks + id);
-            } else {
-                signalHandler();
-            }
-        }
-
-        if (eventCount != -1) writeStatus(&status);
-    }
-    freeStatus(&status);
-}
-
-void init() {
-    epollFD = epoll_create(blockCount);
-    struct epoll_event event = {
-        .events = EPOLLIN,
-    };
-
-    for (int i = 0; i < blockCount; i++) {
-        // Append each block's pipe's read end to `epollFD`
-        pipe(blocks[i].pipe);
-        event.data.u32 = i;
-        epoll_ctl(epollFD, EPOLL_CTL_ADD, blocks[i].pipe[0], &event);
-
-        // Calculate the max interval and tick size for the timer
-        if (blocks[i].interval) {
-            maxInterval = MAX(blocks[i].interval, maxInterval);
-            timerTick = gcd(blocks[i].interval, timerTick);
-        }
-    }
-
-    setupSignals();
-
-    // Watch signal file descriptor as well
-    event.data.u32 = blockCount;
-    epoll_ctl(epollFD, EPOLL_CTL_ADD, signalFD, &event);
-}
-
-int main(const int argc, const char *argv[]) {
-    if (setupX()) {
-        fprintf(stderr, "%s\n", "dwmblocks: Failed to open display");
+static int init_blocks(void) {
+    for (unsigned short i = 0; i < LEN(blocks); ++i) {
+        block *const block = &blocks[i];
+        if (block_init(block) != 0) {
             return 1;
         }
-
-    for (int i = 0; i < argc; i++) {
-        if (!strcmp("-d", argv[i])) {
-            debugMode = 1;
-            break;
     }
-    }
-
-    init();
-    statusLoop();
-
-    if (closeX())
-        fprintf(stderr, "%s\n", "dwmblocks: Failed to close display");
-
-    close(epollFD);
-    close(signalFD);
-    for (int i = 0; i < blockCount; i++) closePipe(blocks[i].pipe);
 
     return 0;
 }
+
+static int deinit_blocks(void) {
+    for (unsigned short i = 0; i < LEN(blocks); ++i) {
+        block *const block = &blocks[i];
+        if (block_deinit(block) != 0) {
+            return 1;
+        }
+    }
+
+    return 0;
+}
+
+static int execute_blocks(const unsigned int time) {
+    for (unsigned short i = 0; i < LEN(blocks); ++i) {
+        block *const block = &blocks[i];
+        if (!block_must_run(block, time)) {
+            continue;
+        }
+
+        if (block_execute(&blocks[i], 0) != 0) {
+            return 1;
+        }
+    }
+
+    return 0;
+}
+
+static int trigger_event(timer *const timer) {
+    if (execute_blocks(timer->time) != 0) {
+        return 1;
+    }
+
+    if (timer_arm(timer) != 0) {
+        return 1;
+    }
+
+    return 0;
+}
+
+static int refresh_callback(void) {
+    if (execute_blocks(0) != 0) {
+        return 1;
+    }
+
+    return 0;
+}
+
+static int event_loop(const bool is_debug_mode,
+                      x11_connection *const connection,
+                      signal_handler *const signal_handler) {
+    timer timer = timer_new();
+
+    // Kickstart the event loop with an initial execution.
+    if (trigger_event(&timer) != 0) {
+        return 1;
+    }
+
+    watcher watcher;
+    if (watcher_init(&watcher, signal_handler->fd) != 0) {
+        return 1;
+    }
+
+    status status = status_new();
+    bool is_alive = true;
+    while (is_alive) {
+        const int event_count = watcher_poll(&watcher, -1);
+        if (event_count == -1) {
+            return 1;
+        }
+
+        int i = 0;
+        for (unsigned short j = 0; j < WATCHER_FD_COUNT; ++j) {
+            if (i == event_count) {
+                break;
+            }
+
+            const watcher_fd *const watcher_fd = &watcher.fds[j];
+            if (!watcher_fd_is_readable(watcher_fd)) {
+                continue;
+            }
+
+            ++i;
+
+            if (j == SIGNAL_FD) {
+                is_alive = signal_handler_process(signal_handler, &timer) == 0;
+                continue;
+            }
+
+            block *const block = &blocks[j];
+            (void)block_update(block);
+        }
+
+        const bool has_status_changed = status_update(&status);
+        if (has_status_changed) {
+            if (status_write(&status, is_debug_mode, connection) != 0) {
+                return 1;
+            }
+        }
+    }
+
+    return 0;
+}
+
+int main(const int argc, const char *const argv[]) {
+    cli_arguments cli_args;
+    if (cli_init(&cli_args, argv, argc) != 0) {
+        return 1;
+    }
+
+    x11_connection *const connection = x11_connection_open();
+    if (connection == NULL) {
+        return 1;
+    }
+
+    int status = 0;
+    if (init_blocks() != 0) {
+        status = 1;
+        goto x11_close;
+    }
+
+    signal_handler signal_handler =
+        signal_handler_new(refresh_callback, trigger_event);
+    if (signal_handler_init(&signal_handler) != 0) {
+        status = 1;
+        goto deinit_blocks;
+    }
+
+    if (event_loop(cli_args.is_debug_mode, connection, &signal_handler) != 0) {
+        status = 1;
+    }
+
+    if (signal_handler_deinit(&signal_handler) != 0) {
+        status = 1;
+    }
+
+deinit_blocks:
+    if (deinit_blocks() != 0) {
+        status = 1;
+    }
+
+x11_close:
+    x11_connection_close(connection);
+
+    return status;
+}

src/signal-handler.c

@@ -0,0 +1,119 @@
+#include "signal-handler.h"
+
+#include <bits/stdint-uintn.h>
+#include <bits/types/sigset_t.h>
+#include <signal.h>
+#include <stdio.h>
+#include <sys/signalfd.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include "block.h"
+#include "main.h"
+#include "timer.h"
+#include "util.h"
+
+typedef struct signalfd_siginfo signal_info;
+
+signal_handler signal_handler_new(
+    const signal_refresh_callback refresh_callback,
+    const signal_timer_callback timer_callback) {
+    signal_handler handler = {
+        .refresh_callback = refresh_callback,
+        .timer_callback = timer_callback,
+    };
+
+    return handler;
+}
+
+int signal_handler_init(signal_handler *const handler) {
+    signal_set set;
+    (void)sigemptyset(&set);
+
+    // Handle user-generated signal for refreshing the status.
+    (void)sigaddset(&set, REFRESH_SIGNAL);
+
+    // Handle SIGALRM generated by the timer.
+    (void)sigaddset(&set, TIMER_SIGNAL);
+
+    // Handle termination signals.
+    (void)sigaddset(&set, SIGINT);
+    (void)sigaddset(&set, SIGTERM);
+
+    for (unsigned short i = 0; i < LEN(blocks); ++i) {
+        const block *const block = &blocks[i];
+        if (blocks->signal > 0) {
+            if (sigaddset(&set, SIGRTMIN + block->signal) != 0) {
+                (void)fprintf(
+                    stderr,
+                    "error: invalid or unsupported signal specified for "
+                    "\"%s\" block\n",
+                    block->command);
+                return 1;
+            }
+        }
+    }
+
+    // Create a signal file descriptor for epoll to watch.
+    handler->fd = signalfd(-1, &set, 0);
+    if (handler->fd == -1) {
+        (void)fprintf(stderr,
+                      "error: could not create file descriptor for signals\n");
+        return 1;
+    }
+
+    // Block all realtime and handled signals.
+    for (int i = SIGRTMIN; i <= SIGRTMAX; ++i) {
+        (void)sigaddset(&set, i);
+    }
+    (void)sigprocmask(SIG_BLOCK, &set, NULL);
+
+    return 0;
+}
+
+int signal_handler_deinit(signal_handler *const handler) {
+    if (close(handler->fd) != 0) {
+        (void)fprintf(stderr,
+                      "error: could not close signal file descriptor\n");
+    }
+
+    return 0;
+}
+
+int signal_handler_process(signal_handler *const handler, timer *const timer) {
+    signal_info info;
+    const ssize_t bytes_read = read(handler->fd, &info, sizeof(info));
+    if (bytes_read == -1) {
+        (void)fprintf(stderr, "error: could not read info of incoming signal");
+        return 1;
+    }
+
+    const int signal = (int)info.ssi_signo;
+    switch (signal) {
+        case TIMER_SIGNAL:
+            if (handler->timer_callback(timer) != 0) {
+                return 1;
+            }
+            return 0;
+        case REFRESH_SIGNAL:
+            if (handler->refresh_callback() != 0) {
+                return 1;
+            }
+            return 0;
+        case SIGTERM:
+            // fall through
+        case SIGINT:
+            return 1;
+    }
+
+    for (unsigned short i = 0; i < LEN(blocks); ++i) {
+        block *const block = blocks + i;
+        if (block->signal == signal - SIGRTMIN) {
+            const uint8_t button = (uint8_t)info.ssi_int;
+            block_execute(block, button);
+            break;
+        }
+    }
+
+    return 0;
+}

src/status.c

@@ -0,0 +1,74 @@
+#include "status.h"
+
+#include <stdbool.h>
+#include <stdio.h>
+#include <string.h>
+
+#include "block.h"
+#include "config.h"
+#include "main.h"
+#include "util.h"
+#include "x11.h"
+
+static bool has_status_changed(const status *const status) {
+    return strcmp(status->current, status->previous) != 0;
+}
+
+status status_new(void) {
+    status status = {
+        .current = {[0] = '\0'},
+        .previous = {[0] = '\0'},
+    };
+
+    return status;
+}
+
+bool status_update(status *const status) {
+    (void)strcpy(status->previous, status->current);
+    status->current[0] = '\0';
+
+    for (unsigned short i = 0; i < LEN(blocks); ++i) {
+        const block *const block = &blocks[i];
+
+        if (strlen(block->output) > 0) {
+#if LEADING_DELIMITER
+            (void)strcat(status->current, DELIMITER);
+#else
+            if (status->current[0] != '\0') {
+                (void)strcat(status->current, DELIMITER);
+            }
+#endif
+
+#if CLICKABLE_BLOCKS
+            if (block->signal > 0) {
+                const char signal[] = {(char)block->signal, '\0'};
+                (void)strcat(status->current, signal);
+            }
+#endif
+
+            (void)strcat(status->current, block->output);
+        }
+    }
+
+#if TRAILING_DELIMITER
+    if (status->current[0] != '\0') {
+        (void)strcat(status->current, DELIMITER);
+    }
+#endif
+
+    return has_status_changed(status);
+}
+
+int status_write(const status *const status, const bool is_debug_mode,
+                 x11_connection *const connection) {
+    if (is_debug_mode) {
+        (void)printf("%s\n", status->current);
+        return 0;
+    }
+
+    if (x11_set_root_name(connection, status->current) != 0) {
+        return 1;
+    }
+
+    return 0;
+}

src/timer.c

@@ -0,0 +1,56 @@
+#include "timer.h"
+
+#include <errno.h>
+#include <stdio.h>
+#include <unistd.h>
+
+#include "block.h"
+#include "main.h"
+#include "util.h"
+
+static unsigned int compute_tick(void) {
+    unsigned int tick = 0;
+
+    for (unsigned short i = 0; i < LEN(blocks); ++i) {
+        const block *const block = &blocks[i];
+        tick = gcd(block->interval, tick);
+    }
+
+    return tick;
+}
+
+static unsigned int compute_reset_value(void) {
+    unsigned int reset_value = 1;
+
+    for (unsigned short i = 0; i < LEN(blocks); ++i) {
+        const block *const block = &blocks[i];
+        reset_value = MAX(block->interval, reset_value);
+    }
+
+    return reset_value;
+}
+
+timer timer_new(void) {
+    timer timer = {
+        .time = 0,
+        .tick = compute_tick(),
+        .reset_value = compute_reset_value(),
+    };
+
+    return timer;
+}
+
+int timer_arm(timer *const timer) {
+    errno = 0;
+    (void)alarm(timer->tick);
+
+    if (errno != 0) {
+        (void)fprintf(stderr, "error: could not arm timer\n");
+        return 1;
+    }
+
+    // Wrap `time` to the interval [1, reset_value].
+    timer->time = (timer->time + timer->tick) % timer->reset_value + 1;
+
+    return 0;
+}

src/util.c

@@ -1,41 +1,50 @@
 #include "util.h"
 
-#include <unistd.h>
+#include <stdio.h>
+#define UTF8_MULTIBYTE_BIT BIT(7)
 
-int gcd(int a, int b) {
-    int temp;
+unsigned int gcd(unsigned int a, unsigned int b) {
     while (b > 0) {
-        temp = a % b;
+        const unsigned int temp = a % b;
         a = b;
         b = temp;
     }
+
     return a;
 }
 
-void closePipe(int pipe[2]) {
-    close(pipe[0]);
-    close(pipe[1]);
+size_t truncate_utf8_string(char* const buffer, const size_t size,
+                            const size_t char_limit) {
+    size_t char_count = 0;
+    size_t i = 0;
+    while (char_count < char_limit) {
+        char ch = buffer[i];
+        if (ch == '\0') {
+            break;
         }
 
-void trimUTF8(char* buffer, unsigned int size) {
-    int length = (size - 1) / 4;
-    int count = 0, j = 0;
-    char ch = buffer[j];
-    while (ch != '\0' && ch != '\n' && count < length) {
-        // Skip continuation bytes, if any
-        int skip = 1;
-        while ((ch & 0xc0) > 0x80) {
+        unsigned short skip = 1;
+
+        // Multibyte unicode character
+        if ((ch & UTF8_MULTIBYTE_BIT) != 0) {
+            // Skip continuation bytes.
             ch <<= 1;
-            skip++;
+            while ((ch & UTF8_MULTIBYTE_BIT) != 0) {
+                ch <<= 1;
+                ++skip;
+            }
         }
 
-        j += skip;
-        ch = buffer[j];
-        count++;
+        // Avoid buffer overflow.
+        if (i + skip >= size) {
+            break;
         }
 
-    // Trim trailing newline and spaces
-    buffer[j] = ' ';
-    while (j >= 0 && buffer[j] == ' ') j--;
-    buffer[j + 1] = '\0';
+        ++char_count;
+        i += skip;
+    }
+
+    buffer[i] = '\0';
+
+    return i + 1;
 }

src/watcher.c

@@ -0,0 +1,53 @@
+#include "watcher.h"
+
+#include <errno.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <sys/poll.h>
+
+#include "main.h"
+#include "util.h"
+
+int watcher_init(watcher* const watcher, const int signal_fd) {
+    if (signal_fd == -1) {
+        fprintf(stderr,
+                "error: invalid signal file descriptor passed to watcher\n");
+        return 1;
+    }
+
+    watcher_fd* const fd = &watcher->fds[SIGNAL_FD];
+    fd->fd = signal_fd;
+    fd->events = POLLIN;
+
+    for (unsigned short i = 0; i < LEN(blocks); ++i) {
+        const int block_fd = blocks[i].pipe[READ_END];
+        if (block_fd == -1) {
+            fprintf(
+                stderr,
+                "error: invalid block file descriptors passed to watcher\n");
+            return 1;
+        }
+
+        watcher_fd* const fd = &watcher->fds[i];
+        fd->fd = block_fd;
+        fd->events = POLLIN;
+    }
+
+    return 0;
+}
+
+int watcher_poll(watcher* watcher, const int timeout_ms) {
+    const int event_count = poll(watcher->fds, LEN(watcher->fds), timeout_ms);
+
+    // Don't return non-zero status for signal interruptions.
+    if (event_count == -1 && errno != EINTR) {
+        (void)fprintf(stderr, "error: watcher could not poll blocks\n");
+        return -1;
+    }
+
+    return event_count;
+}
+
+bool watcher_fd_is_readable(const watcher_fd* const watcher_fd) {
+    return (watcher_fd->revents & POLLIN) != 0;
+}

src/x11.c

@@ -1,25 +1,44 @@
 #include "x11.h"
 
-#include <X11/Xlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <xcb/xcb.h>
+#include <xcb/xproto.h>
 
-static Display *display;
-static Window rootWindow;
+x11_connection *x11_connection_open(void) {
+    xcb_connection_t *const connection = xcb_connect(NULL, NULL);
+    if (xcb_connection_has_error(connection)) {
+        (void)fprintf(stderr, "error: could not connect to the X server\n");
+        return NULL;
+    }
 
-int setupX() {
-    display = XOpenDisplay(NULL);
-    if (!display) {
+    return connection;
+}
+
+void x11_connection_close(xcb_connection_t *const connection) {
+    xcb_disconnect(connection);
+}
+
+int x11_set_root_name(x11_connection *const connection, const char *name) {
+    xcb_screen_t *const screen =
+        xcb_setup_roots_iterator(xcb_get_setup(connection)).data;
+    const xcb_window_t root_window = screen->root;
+
+    const unsigned short name_format = 8;
+    const xcb_void_cookie_t cookie = xcb_change_property(
+        connection, XCB_PROP_MODE_REPLACE, root_window, XCB_ATOM_WM_NAME,
+        XCB_ATOM_STRING, name_format, strlen(name), name);
+
+    xcb_generic_error_t *error = xcb_request_check(connection, cookie);
+    if (error != NULL) {
+        (void)fprintf(stderr, "error: could not set X root name\n");
+        return 1;
+    }
+
+    if (xcb_flush(connection) <= 0) {
+        (void)fprintf(stderr, "error: could not flush X output buffer\n");
         return 1;
     }
 
-    rootWindow = DefaultRootWindow(display);
     return 0;
 }
-
-int closeX() {
-    return XCloseDisplay(display);
-}
-
-void setXRootName(char *str) {
-    XStoreName(display, rootWindow, str);
-    XFlush(display);
-}